8,590 research outputs found

    Selective attention to conditioned stimuli in human discrimination learning: Untangling the effect of outcome prediction, valence, arousal and uncertainty

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    What are the neural mechanisms underlying this ability? Are they the same in humans as in other animals? And what are the consequences of damage to this attentional system? These are the questions that this book aims to answer.The preparation of this manuscript was supported by a MRC new investigator award to Lee Hogarth (G0701456)

    Plasma Electron Beam Welder for Space Vehicles Final Report

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    Feasibility of developing plasma electron beam welding system for earth orbiting vehicl

    Flying Drosophila maintain arbitrary but stable headings relative to the angle of polarized light

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    Animals must use external cues to maintain a straight course over long distances. In this study, we investigated how the fruit fly Drosophila melanogaster selects and maintains a flight heading relative to the axis of linearly polarized light, a visual cue produced by the atmospheric scattering of sunlight. To track flies' headings over extended periods, we used a flight simulator that coupled the angular velocity of dorsally presented polarized light to the stroke amplitude difference of the animals’ wings. In the simulator, most flies actively maintained a stable heading relative to the axis of polarized light for the duration of 15 min flights. We found that individuals selected arbitrary, unpredictable headings relative to the polarization axis, which demonstrates that D. melanogaster can perform proportional navigation using a polarized light pattern. When flies flew in two consecutive bouts separated by a 5 min gap, the two flight headings were correlated, suggesting individuals retain a memory of their chosen heading. We found that adding a polarized light pattern to a light intensity gradient enhanced flies' orientation ability, suggesting D. melanogaster use a combination of cues to navigate. For both polarized light and intensity cues, flies' capacity to maintain a stable heading gradually increased over several minutes from the onset of flight. Our findings are consistent with a model in which each individual initially orients haphazardly but then settles on a heading which is maintained via a self-reinforcing process. This may be a general dispersal strategy for animals with no target destination

    Spitzer 70 Micron Source Counts in GOODS-North

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    We present ultradeep Spitzer 70 ÎŒm observations of GOODS-North (Great Observatories Origins Deep Survey). For the first time, the turnover in the 70 ÎŒm Euclidean-normalized differential source counts is observed. We derive source counts down to a flux density of 1.2 mJy. From the measured source counts and fluctuation analysis, we estimate a power-law approximation of the faint 70 ÎŒm source counts of dN/dS ∝ S^−1.6, consistent with that observed for the faint 24 ÎŒm sources. An extrapolation of the 70 ÎŒm source counts to zero flux density implies a total extragalactic background light (EBL) of 7.4 ± 1.9 nW m^−2 sr^−1. The source counts above 1.2 mJy account for about 60% of the estimated EBL. From fluctuation analysis, we derive a photometric confusion level of σc = 0.30 ± 0.15 mJy (q = 5) for the Spitzer 70 ÎŒm band

    CBI limits on 31 GHz excess emission in southern HII regions

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    We have mapped four regions of the southern Galactic plane at 31 GHz with the Cosmic Background Imager. From the maps, we have extracted the flux densities for six of the brightest \hii regions in the southern sky and compared them with multi-frequency data from the literature. The fitted spectral index for each source was found to be close to the theoretical value expected for optically thin free-free emission, thus confirming that the majority of flux at 31 GHz is due to free-free emission from ionised gas with an electron temperature of ≈7000−8000\approx 7000-8000 K. We also found that, for all six sources, the 31 GHz flux density was slightly higher than the predicted value from data in the literature. This excess emission could be due to spinning dust or another emission mechanism. Comparisons with 100ÎŒ100 \mum data indicate an average dust emissivity of 3.3±1.7ÎŒ3.3\pm1.7 \muK (MJy/sr)−1^{-1}, or a 95 per cent confidence limit of <6.1ÎŒ<6.1 \muK (MJy/sr)−1^{-1}. This is lower than that found in diffuse clouds at high Galactic latitudes by a factor of ∌3−4\sim 3-4. The most significant detection (3.3σ3.3\sigma) was found in G284.3−0.3G284.3-0.3 (RCW49) and may account for up to ≈30\approx 30 per cent of the total flux density observed at 31 GHz. Here, the dust emissivity of the excess emission is 13.6±4.2ÎŒ13.6\pm4.2 \muK (MJy/sr)−1^{-1} and is within the range observed at high Galactic latitudes. Low level polarised emission was observed in all six sources with polarisation fractions in the range 0.3−0.60.3-0.6 per cent. This is likely to be mainly due to instrumental leakage and is therefore upper an upper limit to the free-free polarisation. It corresponds to an upper limit of ∌1\sim1 per cent for the polarisation of anomalous emission.Comment: Accepted in MNRAS. 12 pages, 10 figures, 5 table

    An upper limit on anomalous dust emission at 31 GHz in the diffuse cloud [LPH96]201.663+1.643

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    [LPH96]201.663+1.643, a diffuse H{\sc ii} region, has been reported to be a candidate for emission from rapidly spinning dust grains. Here we present Cosmic Background Imager (CBI) observations at 26-36 GHz that show no evidence for significant anomalous emission. The spectral index within the CBI band, and between CBI and Effelsberg data at 1.4/2.7 GHz, is consistent with optically thin free-free emission. The best-fitting temperature spectral index from 2.7 to 31 GHz, ÎČ=−2.06±0.03\beta=-2.06 \pm 0.03, is close to the theoretical value, ÎČ=−2.12\beta=-2.12 for Te=9100T_{e}=9100 K. We place an upper limit of 24% ~ (2\sigma) for excess emission at 31 GHz as seen in a 6\arcmin FWHM beam. Current spinning dust models are not a good fit to the spectrum of LPH96. No polarized emission is detected in the CBI data with an upper limit of 2% on the polarization fraction.Comment: 5 pages, 3 figures, submitted to ApJ

    Senior Programmers: Characteristics of Elderly Users from Stack Overflow

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    In this paper we presents results of research about elderly users of Stack Overflow (Question and Answer portal for programmers). They have different roles, different main activities and different habits. They are an important part of the community, as they tend to have higher reputation and they like to share their knowledge. This is a great example of possible way of keeping elderly people active and helpful for society
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